Re: [CFR][PATCH] drm2: don't assume that dev->driver->max_ioctl > *dev->driver->compat_ioctls_nr

Fri, Nov 28, 2014 at 07:32:26PM +0200, Konstantin Belousov wrote:
> On Fri, Nov 28, 2014 at 04:29:42PM +0300, Eygene Ryabinkin wrote:
> > I noticed that the current ioctl processing code for drm2 implicitely
> > assumes that the number of native ioctls is higher than that of 32-bit
> > compat ones, so it immediately gives EINVAL when
> > nr >= dev->driver->max_ioctl.  Seems that in future such assumption
> > may not be true in all cases.
>
> I very much doubt that it could become true. Compat32 ioctl cannot
> exist without its wider counterpart.

OK.

> > This can be fixed with the following patch:
> >   http://codelabs.ru/fbsd/patches/drm2/drm_drv-untangle-32bit-compat.diff
> > 
> > Any thoughts on it?
>
> I think either current way or patch are fine, but why changing something
> which is fine ?

Because the patched code will work with less assumptions and the patch
isn't big or complex and introduces no additional code paths, just
rearranges things.  It also has more unified logics: if 32-bit compat
is present and ioctl fits into its range -- do that.  If ioctl fits
into the native driver ioctl range -- do that.  Otherwise -- bail out
with an error.  And "if" conditions are more uniform w.r.t. check
for value of "nr".
-- 
Eygene Ryabinkin                                        ,,,^..^,,,
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